The battery voltage drops when there is no available PV power.
Is the battery already faulty/defective?
Battery is a lead-acid AGM.
asked
Battery Voltage drops when there is no PV power/voltage/Current
That looks fairly normal to me, though your battery is not fully charged,
The battery should reach absorption voltage at ~11am and then hold it for some time (1 hour) before remaining at float voltage until the afternoon.
In your example here - it doesn't look like it is reaching Absorption voltage at all - so that is not good - but not the end of the battery.
The good news is it DOES look like the battery is absorbing the charge current - which a failing battery will not do (with battery voltage spiking quickly and not allowing much current to charge).
Please take the Lead Acid Battery Online Training course to learn more about normal battery behaviour, and how to ensure long life.
A MUCH better test of battery health is the response to a large load.
